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Sökning: WFRF:(Löthberg Peter)

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1.
  • Ebenhag, Sven-Christian, 1976-, et al. (författare)
  • Measurements and Error Sources in Time Transfer Using Asynchronous Fiber Network
  • 2010
  • Ingår i: IEEE Transactions on instrumentation and measurement. - 0018-9456. ; 59:7, s. 1918-1924
  • Tidskriftsartikel (refereegranskat)abstract
    • We have performed time transfer experiments based on passive listening in fiber optical networks using Packet over synchronous optical networking (SONET)/synchronous digital hierarchy(SDH). The experiments have been performed with different complexity and over different distances. For assessment of the results, we have used a GPS link based on carrier-phase observations. On a 560-km link, precision that is relative to the GPS link of < 1 ns has been obtained over several months. In this paper, we describe and quantify the different error sources influencing the fiber time transfer measurements. We show that the temperature dependence of the optical fiber is the major contribution to the error budget, and, thus, reducing this effect should be the best way of improving the results.
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2.
  • Ebenhag, Sven-Christian, 1976-, et al. (författare)
  • Time Transfer between UTC(SP) and UTC(MIKE) Using Frame Detection in Fiber-Optical Communication networks
  • 2011
  • Ingår i: 43rd Precise Time and Time Interval (PTTI) Systems and Applications Meeting.
  • Konferensbidrag (refereegranskat)abstract
    • This paper presents recent results from a time transfer method using passive listening and detection of SDH frame headers in fiber-optical networks. The results are based on an experimental fiber-link that is implemented between the national time and frequency laboratories at SP in Borås, Sweden and at MIKES in Espoo, Finland with an intermediate connection at STUPI time and frequency facility in Stockholm, Sweden. The total fiber length exceeds 1129 km and is implemented in SUNET (Swedish University Network) and FUNET (Finnish University and Research Network). The two networks are connected via NORDUnet (Nordic Infrastructure for Research & Education) and the links are DWDM-based (Dense Wavelength Division Multiplexing). Both SP and MIKES maintains local representations of UTC and contributes with clock data to TAI, which gives the opportunity to compare the fiber-based method with those independent methods that are used regularly by the laboratories for the links to UTC. Preliminary results show that a time transfer stability of less than 10 picoseconds is obtained for averaging times of a few hundred seconds. The results also show that the method suffers from daily variations of a few nanoseconds, presumable due to temperature sensitive network equipment and asymmetric fiber paths. Nevertheless, a comparison to GPS carrier phase time transfer over three months shows an rms-agreement of less than 1 nanosecond.
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3.
  • Ebenhag, Sven-Christian, 1976-, et al. (författare)
  • TIME TRANSFER USING AN ASYNCHRONOUS COMPUTER NETWORK: RESULTS FROM A 500 KM BASELINE EXPERIMENT
  • 2007
  • Ingår i: Topical Meeting on Precise Time and Time Interval, 27-30/11, Long Beach, CA.
  • Konferensbidrag (refereegranskat)abstract
    • SP Technical Research Institute of Sweden and STUPI have performed a time transfer experiment over a 500km long baseline between Borås and Stockholm. The time transfer technique passively utilizes the data bit stream generated in an optical fiber computer network based on the packet over SONET/SDH technique. A small fraction of the optical signal is monitored both at the transmitter and at the receiver. When an occurrence of a unique bit sequence of the SDH frames is detected, an electrical pulse is generated and compared with a resolution of 100 ps to a local clock. With data from all four positions of an optical bidirectional link, two-way time-transfer can be achieved and any symmetrical variations in delay can potentially be cancelled. The results presented here have been obtained over OptoSUNET, the new Swedish University Network. In the experiment, 10 Gbit/s traffic from SP over OptoSUNET is extended in Stockholm to STUPI, a clock laboratory which is the second node in this setup. This reconnection enables that a communication channel is established between two nodes, with no intermediate jump. The time-transfer experiment includes more than 500 km of fiber transmission, of which several km is via air-lines. By comparing the results from a GPS carrierphase link, a precision better than ± 1 ns is achieved over several months of measurements between two Hydrogen-masers.
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4.
  • Ebenhag, Sven-Christian, 1976-, et al. (författare)
  • Time transfer using an asynchronous computer network: Results from three weeks of measurements
  • 2007
  • Ingår i: European Frequency and Time Forum, 29/5 - 1/6, Geneva, CH.
  • Konferensbidrag (refereegranskat)abstract
    • We have performed a time transfer experiment between two atomic clocks, over a distance of approximately 75 km using an 10 Gbit/s asynchronous fiber-optic computer network. The time transfer was accomplished through passive listening on existing data traffic and a pilot sequence in the SDH bit stream. In order to assess the fiber-link clock comparison, we simultaneously compared the clocks using a GPS carrier phase link. The standard deviation of the difference between the two time transfer links over the three-week time period was 243 ps.
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